Homework: Strings and Text Processing
This document defines the homework assignments from the "Advanced C#" Course @ Software University. Please
submit as homework a single zip / rar / 7z archive holding the solutions (source code) of all below described
problems.
Note: You are NOT allowed to use regular expressions in this homework assignment.
Problem 1. Reverse String
Write a program that reads a string from the console, reverses it and prints the result back at the console.
Input
sample
Output
elpmas
24tvcoi92 29iocvt42
Problem 2. String Length
Write a program that reads from the console a string of maximum 20 characters. If the length of the string is less than
20, the rest of the characters should be filled with *. Print the resulting string on the console.
Examples:
Input
Output
Welcome to SoftUni!
Welcome to SoftUni!*
a regular expression (abbreviated regex or regexp and sometimes a regular expression
called a rational expression) is a sequence of characters that
forms a search pattern
C#
C#******************
Problem 3. Count Substring Occurrences
Write a program to find how many times a given string appears in a given text as substring. The text is given at the
first input line. The search string is given at the second input line. The output is an integer number. Please ignore the
character casing. Overlapping between occurrences is allowed. Examples:
Input
Output
Welcome to the Software University (SoftUni)! Welcome to programming. 4
Programming is wellness for developers, said Maxwell.
wel
aaaaaa
aa
5
ababa caba
aba
3
Welcome to SoftUni
Java
0
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Problem 4. Text Filter
Write a program that takes a text and a string of banned words. All words included in the ban list should be replaced
with asterisks "*", equal to the word's length. The entries in the ban list will be separated by a comma and space ", ".
The ban list should be entered on the first input line and the text on the second input line. Example:
Input
Output
Linux, Windows
It is not *****, it is GNU/*****. *****
It is not Linux, it is GNU/Linux. Linux is is merely the kernel, while GNU adds the
merely the kernel, while GNU adds the functionality. Therefore we owe it to them
functionality. Therefore we owe it to them by calling the OS GNU/*****! Sincerely, a
by calling the OS GNU/Linux! Sincerely, a ******* client
Windows client
Problem 5. Unicode Characters
Write a program that converts a string to a sequence of C# Unicode character literals. Examples:
Input
Output
Hi!
\u0048\u0069\u0021
What?!?
\0057\0068\0061\0074\003f\0021\003f
SoftUni
\0053\006f\0066\0074\0055\006e\0069
Problem 6. Palindromes
Write a program that extracts from a given text all palindromes, e.g. ABBA, lamal, exe and prints them on the console
on a single line, separated by comma and space. Use spaces, commas, dots, question marks and exclamation marks
as word delimiters. Print only unique palindromes, sorted lexicographically.
Example:
Input
Output
Hi,exe? ABBA! Hog fully a string. Bob a, ABBA, exe
Problem 7. * Letters change Numbers
This problem is from the Java Basics exam (8 February 2015). You may check your solution here.
Nakov likes Math. But he also likes the English alphabet a lot. He invented a game with numbers and letters from the
English alphabet. The game was simple. You get a string consisting of a number between two letters. Depending on
whether the letter was in front of the number or after it you would perform different mathematical operations on the
number to achieve the result.
First you start with the letter before the number. If it's Uppercase you divide the number by the letter's position in
the alphabet. If it's lowercase you multiply the number with the letter's position. Then you move to the letter after
the number. If it's Uppercase you subtract its position from the resulted number. If it's lowercase you add its position
to the resulted number. But the game became too easy for Nakov really quick. He decided to complicate it a bit by
doing the same but with multiple strings keeping track of only the total sum of all results. Once he started to solve
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this with more strings and bigger numbers it became quite hard to do it only in his mind. So he kindly asks you to write
a program that calculates the sum of all numbers after the operations on each number have been done.
For example, you are given the sequence "A12b s17G". We have two strings – "A12b" and "s17G". We do the
operations on each and sum them. We start with the letter before the number on the first string. A is Uppercase and
its position in the alphabet is 1. So we divide the number 12 with the position 1 (12/1 = 12). Then we move to the
letter after the number. b is lowercase and its position is 2. So we add 2 to the resulted number (12+2=14). Similarly
for the second string s is lowercase and its position is 19 so we multiply it with the number (17*19 = 323). Then we
have Uppercase G with position 7, so we subtract it from the resulted number (323 – 7 = 316). Finally we sum the 2
results and we get 14 + 316=330;
Input
The input comes from the console as a single line, holding the sequence of strings. Strings are separated by one or
more white spaces.
The input data will always be valid and in the format described. There is no need to check it explicitly.
Output
Print at the console a single number: the total sum of all processed numbers rounded up to two digits after the
decimal separator.
Constraints



The count of the strings will be in the range [1 … 10].
The numbers between the letters will be integers in range [1 … 2 147 483 647].
Time limit: 0.3 sec. Memory limit: 16 MB.
Examples
Input
Output
A12b s17G
P34562Z q2576f
a1A
330.00
H456z
Comment
12/1=12, 12+2=14, 17*19=323, 323–7=316, 14+316=330
46015.13
0.00
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